West Nile Virus Death Raises Transfusion Issues

In the first documented case of its kind, an immunocompromised patient died from a West Nile virus (WNV) infection most likely contracted through a blood transfusion, researchers found.

The patient -- a man with non-Hodgkin's lymphoma -- had been given blood donation that was part of a "minipool" of six donations. As a group, the donations were reactive for WNV but each had tested negative individually, according to Ingrid Rabe, MBChB, of the CDC's Division of Vector-Borne Diseases in Fort Collins, Colo., and colleagues.

There have been no other cases of WNV transmission through a transfusion after the blood product was cleared by individual testing, they reported in the Aug. 9 issue of Morbidity and Mortality Weekly Report.

"Although WNV is rarely transmitted through screened blood products, clinicians should consider WNV disease in patients with compatible symptoms who were recently transfused," particularly those who are immunocompromised, the authors wrote.

The relative risks and benefits of different strategies for managing minipools that are reactive as a group but in which all of the component donations are negative on individual screening need to be evaluated further, they wrote.

In this particular case, "the blood collection and testing agencies involved have now decided to discard all constituent units of reactive minipools when an [individually] reactive donation cannot be identified," Rabe and colleagues noted.

WNV is typically transmitted by mosquitoes but it can also be spread through infected blood or solid organs. Because of that threat, the U.S. blood supply has been screened for the virus since 2003. The FDA recommends screening all blood donations with nucleic acid testing throughout the year, either in minipools of six or 16 donations or individually.

Since 2003, screening has removed about 3,500 reactive units, although some have occasionally managed to slip through; there have been 12 transfusion-associated WNV cases documented since screening began.

In the latest case, the patient was admitted in August 2012 for chemotherapy and an autologous stem cell transplant. He had been screened for subclinical infections 14 days before stem cell collection and none -- including WNV -- was detected.

The transplant occurred on hospital days 8 and 9. The patient developed gastrointestinal symptoms on day 18 and then fever and hypotension on day 28. A day later, he developed altered mental status, somnolence, and respiratory distress.

A cerebrospinal fluid sample taken on day 30 was negative for various bacterial and viral infections, but it wasn't tested for West Nile.

The patient's mental status did not improve and he ultimately died on day 47. Diffuse encephalitis was revealed on the postmortem evaluation.

After the fact, WNV was detected in serum that had been collected on day 43 and in brain and spinal cord tissues collected during autopsy. Because of the timing of the onset of symptoms, public health officials determined that mosquito-borne transmission of the virus was unlikely.

So investigators looked at the possibility of contaminated blood products. Prior to day 43, the patient had received six units of red blood cells, two units of platelets, and two units of fresh frozen plasma from 10 different donors.

Serologic testing cleared nine of those donors, but one apheresis donor was positive for West Nile virus immunoglobulin M (IgM) antibodies. The donor had not become ill but did report outdoor exposure with mosquito bites.

The specific blood product believed to have caused the infection in the patient underwent the standard screening protocol. It was part of a minipool -- with five other donations -- that was reactive for WNV. However, because all six donations were negative when tested individually, they were released for use as recommended by the FDA.

Retrospective, individual testing of the implicated donation yielded conflicting results from multiple assays. Some of the tests revealed WNV-specific IgM and neutralizing antibodies.

Blood products from the same donor had been used in nine other patients at the hospital. Four died, but the deaths were not considered related to WNV infection. The remaining five were monitored and remained asymptomatic, but they were not tested for WNV.

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